Preheat the oven to 400°F. In a baking dish, arrange the peppers, cut side up. Bake for 10 minutes, to soften slightly. Discard any liquid that may have accumulated in the pepper halves. Leave the oven on.
Set a large skillet over medium heat. Add the oil and butter. When the butter is melted, add the vegan steak tips. Cook for 10 minutes, stirring frequently, until browned. Transfer to a cutting board and cut into thin slices. Set aside.
Add the mushrooms and onion to the hot skillet. Cook for 3 minutes, stirring frequently, until softened. Add the steak slices and steak seasoning. Continue cooking for an additional 2 minutes, stirring frequently.
Remove from heat and stir in 1/2 cup of provolone cheese. Spoon the steak filling into the peppers and top with the remaining 1/4 cup of cheese.
Bake for 15 minutes, then serve hot.